1. Field of the Invention
The present invention relates to a device for reducing the burden of work to attach and detach a heavy wire rope, that is, a hooking work in lifting a large and heavy load.
2. Background Art
In the case of lifting a large load and transporting it to the designated place, it has been a general practice in the conventional art to hook a load to be lifted with wire ropes by the manpower of a hooking worker and then to hoist the wire ropes by hitching them with the crane hook. However, in the case of lifting a heavy load, there has been a problem that a lot of hooking workers are required, the workability becomes bad, the physical sufferings of the workers become extremely large, and the safety in the work is worsened, because the wire ropes having a large diameter and large weight must be employed in such a work.
To solve such a problem, as disclosed in the Gazette of Japanese Patent Laid-Open 58-144086 and the Gazette of Japanese Patent Laid-Open 59-26888 for example, there has been offered heavy load lifting tackles for adjusting automatically the lifting angle between said hooking wire ropes. Those heavy load lifting tackles have such a construction that plural number of arm members are telescopically expanded for adjustment, a lifting plate to which a lifting wire rope is connected is attached to the top end of each of the arm members, a clamp is hung from the bottom of each lifting plate, the clamp is secured near the periphery of a load to be lifted, and then the sloping angle between said arms is changed corresponding to the lifting angle between said lifting wire ropes. And, as a driver for expanding the arms, weights are used in the former example, and springs are used in the latter.
The heavy load lifting tackles offered in said examples are aimed to make a hooking work safe and easy, and proved a relatively large effect in reducing the burden of the hooking workers. However, even in such devices, in the case of former heavy load lifting tackle in which weights are used, for example, there has been a problem that the device itself becomes a heavy load and difficult to handle because it includes heavy weight.
In the case of the heavy load lifting tackle of the latter example in which springs are used, there has been a large problem that ready-made wire ropes can't be used because the shaft member which supports the springs projects downwards to make the lift of the overall device high. In addition, said lifting tackle has been including a serious obstacle to a practical use that the device itself is heavy, the manufacturing cost is high, and the handling is difficult because the device has a complicated construction.
Further, there have been problems that the clamp which is hung from the lifting plate, though coming near the periphery of the load to be lifted, is easy to swing, with the shackle installed on the lifting plate being a supporting point, and that the clamp once bit the load to be lifted comes off from the load, or the clamp can't be removed automatically from the load after the completion of transportation. These problems become serious especially in hooking a load to be lifted directly with wire rope without using a clamp and, in such a case, the wire rope which is engaging the load to be lifted must be held by a hooking worker when lifting or lowering the crane hook, and it must also be removed from the load by the manpower of a hooking worker. Therefore, a hooking worker has been required to carry out the same work as that in the conventional art, and there has been a limit in reducing the burden of the hooking worker